Image exposure method for mobile terminal based on eyeprint recognition and image exposure system

ABSTRACT

An image exposure method for a mobile terminal may be based on eyeprint recognition and an image exposure system, wherein the image exposure method may include acquiring image data through a camera when it is detected that the mobile terminal turns on the eyeprint recognition; positioning an eyeball at an eyeball position, and acquiring a brightness parameter of the eyeball position; and querying a prestored exposure parameter corresponding to the acquired brightness parameter, adjusting the exposure parameter, and exposing the eyeball at the eyeball position according to the adjusted exposure parameter.

TECHNICAL FIELD

The present invention relates to the field of mobile terminaltechnologies, and more particularly, to an image exposure method for amobile terminal based on eyeprint recognition and an image exposuresystem.

BACKGROUND

With the development of mobile communication and continuous improvementof living standards, use of various mobile terminals, such as mobilephones, is becoming increasingly popular, and mobile phones have becomean indispensable means of communication in people's daily lives.

With the popularization of smart phones, many users utilize lock screensoftware to protect their privacy on their mobile phones, beautify theirmobile phones, and reduce misoperation.

Eyeprint recognition lock screen software is lock screen software forprotecting privacy on users' mobile phones. Each person's eye texture isdifferent, and less likely to change greatly, in general. The eyeprintrecognition lock screen software utilizes this principle to determinewhether or not a user is an owner of the mobile phone by means ofeyeprint analysis.

The use procedures of the eyeprint recognition lock screen software areas below: in using for the first time, the user must input his/her owneyeprint information, which is similar to face recognition lock screensoftware. Also an alternative unlock method needs to be inputted. Thisis because image recognition lock screen software has a certainprobability of failure in unlocking the screen. An alternative unlockmethod such as a password or nine-grid pattern is preset so that thealternative unlock method is enabled once the eyeprint recognition isfailed.

The principle of the eyeprint recognition lock screen software is asbelow: a plurality of eye images of the user are acquired by using afront-facing camera, then data processing is performed on these imagesto acquire the user's eyeprint information, and the eyeprint informationis stored in the mobile phone locally. When the user unlocks the mobilephone, the eyeprint recognition software may turn on the front-facingcamera to reacquire the user's eyeprint information, and then it isdetermined whether or not the user is the owner of the mobile phone bycomparing the eyeprint recognition with the prestored eyeprintinformation.

The eyeprint recognition lock screen software utilizes a front-facingcamera to acquire eye image information of the user, and then processesand analyzes the image data. Therefore, requirements for image qualityfrom the front-facing camera are relatively higher.

However, different regions of the same image may have a problem ofdifferent exposure levels, resulting in the inability to obtain correctexposure configuration, the eye being too dark or too bright, poor imagequality, lowered eyeprint recognition speed, and inconvenience of theuser in unlocking.

Therefore, the prior art needs to be improved and developed.

SUMMARY

The technical problem to be solved by the present invention, aiming atthe foregoing disadvantages of the prior art, is to provide an imageexposure method for a mobile terminal based on eyeprint recognition andan exposure system. It is intended to solve the disadvantages of failureof eyeprint recognition or slower eyeprint recognition speed due tounderexposure or overexposure in the prior art, when eyeprintrecognition is adopted in a user's mobile terminal.

In order to solve the technical problem, the present invention adoptsthe following technical solutions.

There is provided an image exposure method for a mobile terminal basedon eyeprint recognition, including:

A: detecting whether eyeprint recognition unlocking is started or not;

B: if the eyeprint recognition unlocking is started, turning on thecamera to acquire a user's face image and display by preview theacquired face image on a display screen;

C: processing the face image by using eyeprint recognition software toposition an eyeball position of the face image;

D: acquiring a brightness parameter of the eyeball position according tothe eyeball position;

E: querying a prestored exposure parameter corresponding to thebrightness parameter according to the acquired brightness parameter, andadjusting the queried exposure parameter so that a brightness of animage exposed by using the adjusted exposure parameter is 128gray-levels;

F: exposing the eyeball position according to the adjusted exposureparameter; and

G: matching an eyeprint image acquired after exposure with prestoredeyeprint data, and unlocking the mobile terminal if the matchingsucceeds, or prompting a failure in unlocking if the matching fails.

Further, in Step E, a specific method for adjusting the queried exposureparameter includes: increasing signal amplification factor and exposuretime if the brightness parameter is less than 128 gray-levels; andreducing the signal amplification factor and the exposure time if thebrightness parameter is greater than 128 gray-levels.

The present invention further provides an image exposure method for amobile terminal based on eyeprint recognition, including:

A: acquiring image data through a camera when it is detected that themobile terminal turns on the eyeprint recognition;

B: positioning an eyeball position through image processing, andacquiring a brightness parameter of the eyeball position;

C: querying a prestored exposure parameter corresponding to thebrightness parameter according to the acquired brightness parameter,adjusting the exposure parameter, and exposing the eyeball positionaccording to the adjusted exposure parameter.

In the image exposure method for a mobile terminal based on eyeprintrecognition, before the Step A, the method further includes:

S: acquiring in advance and storing a corresponding relation among auser's eyeprint data, a brightness parameter and an exposure parameter.

In the image exposure method for a mobile terminal based on eyeprintrecognition, after the Step C, the method further includes:

D: verifying an image acquired after exposure with prestored eyeprintdata to unlock the mobile terminal.

In the image exposure method for a mobile terminal based on eyeprintrecognition, the Step C specifically includes:

C1: querying a prestored exposure parameter corresponding to thebrightness parameter according to the acquired brightness parameter;

C2: decreasing or increasing exposure time and signal amplificationfactor according to the corresponding relation; and

C3: exposing the eyeball position according to the adjusted exposureparameter.

In any one of the foregoing image exposure methods for a mobile terminalbased on eyeprint recognition,

the eyeball used during eyeprint recognition may be a left eye or/and aright eye.

The present invention further provides an image exposure system for amobile terminal based on eyeprint recognition, including:

a detecting and acquiring module, configured to acquire image datathrough a camera when it is detected that the mobile terminal turns onthe eyeprint recognition;

a positioning module, configured to position an eyeball position throughimage processing, and acquire a brightness parameter of the eyeballposition;

an adjusting and exposing module, configured to query a prestoredexposure parameter corresponding to the brightness parameter accordingto the acquired brightness parameter, adjust the exposure parameter, andexpose the eyeball position according to the adjusted exposureparameter.

The image exposure system for a mobile terminal based on eyeprintrecognition further includes:

a prestoring module, configured to acquire in advance and store acorresponding relation among a user's eyeprint data, a brightnessparameter and an exposure parameter.

The image exposure system for a mobile terminal based on eyeprintrecognition further includes:

a verifying and unlocking module, configured to verify an image acquiredafter exposure with prestored eyeprint data to unlock the mobileterminal.

In the image exposure system for a mobile terminal based on eyeprintrecognition, the adjusting and exposing module includes:

a querying unit, configured to query a prestored exposure parametercorresponding to the brightness parameter according to the acquiredbrightness parameter;

an adjusting unit, configured to decrease or increase exposure time andsignal amplification factor according to the corresponding relation; and

an exposing module, configured to expose the eyeball position accordingto the adjusted exposure parameter.

In any one of the foregoing image exposure systems for a mobile terminalbased on eyeprint recognition, the eyeball used during eyeprintrecognition may be a left eye or/and a right eye.

The present invention provides an image exposure method for a mobileterminal based on eyeprint recognition and an image exposure system,where the image exposure method includes: acquiring image data through acamera when it is detected that the mobile terminal turns on theeyeprint recognition; positioning an eyeball position through imageprocessing, and acquiring a brightness parameter of the eyeballposition; and according to the acquired brightness parameter, querying aprestored exposure parameter corresponding to the brightness parameter,adjusting the exposure parameter, and exposing the eyeball positionaccording to the adjusted exposure parameter. According to the presentinvention, in the process of eyeprint recognition, a region exposuremethod is used for a user's eyeball exposure to control the exposure, sothat the eyeprint recognition speed is improved, the unlocking is saferand more convenient, and convenience is provided for the user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of an image exposure method for a mobile terminalbased on eyeprint recognition according to a preferred embodiment of thepresent invention;

FIG. 2 is a flowchart of an image exposure method for a mobile terminalbased on eyeprint recognition according to a specific applicationembodiment of the present invention; and

FIG. 3 is a functional block diagram of an image exposure system for amobile terminal based on eyeprint recognition according to a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the objectives, technical solutions, and advantages of thepresent invention clearer, the following further describes in detail thepresent invention with reference to the accompanying drawings andembodiments. It is to be understood that the embodiments describedherein are only intended to explain the present invention, and are notrestrictive of the present invention.

As shown in FIG. 1, the image exposure method for a mobile terminalbased on eyeprint recognition according to a first embodiment of thepresent invention includes:

Step S100: Acquire image data through a camera when it is detected thatthe mobile terminal turns on the eyeprint recognition.

During a concrete implementation, the mobile terminal turns on thecamera to acquire an image when the user starts the eyeprint recognitionunlocking. Preferably, human face data is acquired by the front-facingcamera and data is displayed by preview on a display screen of themobile terminal.

Specifically, before the Step S100, the method further includes:

S1: Acquire in advance and store a corresponding relation among a user'seyeprint data, a brightness parameter and an exposure parameter.

During a concrete implementation, the user sets the method for unlockingthe mobile terminal as the eyeprint recognition unlocking. Each humaneye has two eyeprints, respectively positioned at two sides of an iris.An eyeprint may reveal a great deal of human physiological informationsuch as blood vessels or veins, etc. This seemingly irrelevant databecomes precisely the important index for identifying the user. A smartmobile terminal may capture human eyeprint information.

When it is set as the eyeprint recognition unlocking, the mobileterminal captures the user's eyeprint data and stores the capturedeyeprint data for subsequent eyeprint recognition. Here, the user'seyeprint data may be directly acquired through the camera of the mobileterminal, or be acquired by using a camera and stored in the mobileterminal. Preferably, the user's eyeprint data is directly acquiredthrough the camera of the mobile terminal.

The concrete corresponding relation between the brightness parameter andthe exposure parameter is measured and obtained by many experiments.Preferably, in the present invention, the Y value (namely, thebrightness value) of an image in YUV Space is defined as 128 (athreshold value). When the Y value in the image is greater than orsmaller than 128, the exposure parameters including exposure time andgain (namely, signal amplification factor) are adjusted so that the Yvalue is equal to 128.

A target brightness value is about 18 degree gray (gray-level 128). Ifthe brightness of an image does not reach this brightness value, gain(signal amplification factor) and exposure time are increased so thatthe brightness of the image reaches this target value. Conversely, thegain and the exposure time are decreased if the brightness of the imageis greater than the brightness value. A specific signal amplificationfactor may be 1, 2 and 3, etc. For example, it may be judged whether toincrease or decrease the exposure time and whether to increase thesignal amplification factor or not by means of the difference valuebetween an existing brightness value and the target brightness value.For example, when the Y value (namely, gray-level) of the existingbrightness is 12, the exposure time may be increased by 10 ms, and thesignal amplification factor is tripled. Specifically, adjustment of theexposure time and the signal amplification factor is determinedaccording to the needs.

Step S200: Position an eyeball position through image processing, andacquire a brightness parameter of the eyeball position.

During a concrete implementation, when the camera is turned on, themobile terminal previews human face information. Eyeball position ispositioned through image processing; there are many concrete methods forimage processing in the prior art, which is not unnecessarily describedherein. After positioning the eyeball position by using an imageprocessing method, the mobile terminal also acquires the brightnessparameter of the eyeball position.

Step S300: Query a prestored exposure parameter corresponding to thebrightness parameter according to the acquired brightness parameter,adjust the exposure parameter, and expose the eyeball position accordingto the adjusted exposure parameter.

The Zone System refers to dividing the tone or gray scale of ablack-and-white picture into ten “zones”: from the zero zone (thedarkest part that can be manifested by a photo paper) to the tenth zone(the ground color of the photo paper-white). The fifth zone is mediumgray, which may be acquired by exposure from a reading of a light meter.The fifth zone is a zone whose luminous reflectance is 18%.

A standard practice for acquiring correct exposure for the camera is tocalculate the mean value of Y values of the current image in YUV Space.It is believed that correct exposure is obtained after various exposureparameters settings are adjusted (automatically or manually) so that themean value falls near a target value. In the present invention, 18% grayis defined as a mean value. Generally, it is believed that indoor oroutdoor landscapes have an average luminous reflectance of about 18%.However, as previously mentioned, a color mean value may be regarded asa medium gray tone. Hence, by shooting a gray card having a luminousreflectance of 18%, the exposure parameters are adjusted so that itscolor is close to medium-bright gray (the Y value is 128). Afterward,correct exposure may be automatically obtained for ordinary landscapes.

Therefore, after the brightness parameters of landscapes are acquired,exposure thereof is adjusted close to medium-bright gray to obtain thebest exposure effect. During a concrete implementation, the Step S300specifically includes:

S301: Query a prestored exposure parameter corresponding to thebrightness parameter according to the acquired brightness parameter;

S302: Decrease or increase exposure time and gain according to thecorresponding relation; and

S303: Expose the eyeball position according to the adjusted exposureparameter.

Because an image of blood vessels in the white part of the eyes is usedfor eyeprint recognition, the position of the eyes may be foundaccording to an algorithm, and exposure is adjusted in reference to thewhite part of the eyes.

Excessive exposure may lose eyeprint information. Low exposure mayguarantee acquisition of clearer eyeprint information, and therecognition rate may be increased.

After the Step S300, the method further includes:

Step S400: Verify an image acquired after exposure with prestoredeyeprint data to unlock the mobile terminal. Specifically, an eyeprintimage acquired after exposure is compared and verified with theprestored eyeprint data, the mobile terminal is unlocked if the matchingsucceeds, or a failure in unlocking is prompted if the matching fails.

The eyeball used during eyeprint recognition in the present inventionmay be a left eye or/and a right eye. During a concrete implementation,in a yin-yang face environment, exposure of the user's right and lefteyes is different. Therefore, exposure control may be focused on one eyeto acquire a high-quality image of the eye, and eye recognition isapplied to the eye to accelerate the recognition speed. Also, eyeprintrecognition may be applied to both right and left eyes. It does notspecifically limit how many eyes are used for eyeprint recognition.

In a specific application embodiment of an image exposure method for amobile terminal based on eyeprint recognition according to the presentinvention, as shown in FIG. 2, the method includes following steps:

Step S10: Detect whether the mobile terminal starts the eyeprintrecognition unlocking or not, then execute Step S20;

Step S20: The eyeprint recognition turns on the camera to start previewand acquire image data, then execute Step S30;

Step S30: the eyeprint recognition software processes the image, findsthe position of eyes, and transmits position information to the hardwareabstraction layer of the camera, then execute Step S40;

Step S40: the hardware abstraction layer of the camera performs exposureparameter calculation and configuration on the brightness of theposition; execute Step S50 if the brightness is higher, or execute StepS60 if the brightness is lower; specifically, higher or lower brightnessis relatively, where it is believed that the brightness is lower if aluminous reflectance of an object is less than 18%, and it is believedthat the brightness is higher if the luminous reflectance of the objectis greater than 18%.

Step S50: Reduce exposure time and gain, then execute Step S70;

Step S60: Increase the exposure time and the gain, then execute StepS70;

Step S70: The eyeprint recognition software acquires a better image foreyeprint recognition verification and unlocking, then execute Step S80;

Step S80: Turn off the camera, then execute Step S90; and

Step S90: End eyeprint recognition.

As seen from the foregoing embodiments, the present invention providesan image exposure method for a mobile terminal based on eyeprintrecognition, in the process of eyeprint recognition, a human eyeball isacquired by image processing, and the exposure parameters of the cameraare adjusted according to brightness data of the human eyeball position,and finally a high-quality eyeprint image is obtained for recognitionverification, thereby improving the speed of eyeprint recognition andbringing convenience for the user.

Based on the foregoing embodiments, the present invention furtherprovides a functional block diagram of an image exposure system for amobile terminal based on eyeprint recognition according to a preferredembodiment of the present invention, as shown in FIG. 3, the systemincludes:

a detecting and acquiring module 510, configured to acquire image datathrough a camera when it is detected that the mobile terminal turns onthe eyeprint recognition, specifically as mentioned above;

a positioning module 520, configured to position an eyeball positionthrough image processing, and acquire a brightness parameter of theeyeball position, specifically as mentioned above; and

an adjusting and exposing module 530, configured to query a prestoredexposure parameter corresponding to the brightness parameter accordingto the acquired brightness parameter, adjust the exposure parameter, andexpose the eyeball position according to the adjusted exposureparameter, specifically as mentioned above.

The image exposure system for a mobile terminal based on eyeprintrecognition further includes:

a prestoring module, configured to acquire in advance and store acorresponding relation among a user's eyeprint data, a brightnessparameter and an exposure parameter, specifically as mentioned above.

The image exposure system for a mobile terminal based on eyeprintrecognition further includes:

a verifying and unlocking module, configured to verify an image acquiredafter exposure with prestored eyeprint data to unlock the mobileterminal, specifically as mentioned above.

In the image exposure system for a mobile terminal based on eyeprintrecognition, the adjusting and exposing module includes:

a querying unit, configured to query a prestored exposure parametercorresponding to the brightness parameter according to the acquiredbrightness parameter, specifically as mentioned above;

an adjusting unit, configured to decrease or increase exposure time andgain according to the corresponding relation, specifically as mentionedabove; and

an exposing module, configured to expose the eyeball position accordingto the adjusted exposure parameter, specifically as mentioned above.

In any one of the foregoing image exposure systems for a mobile terminalbased on eyeprint recognition, the eyeball used during eyeprintrecognition may be a left eye or/and a right eye, specifically asmentioned above.

In conclusion, the present invention provides an image exposure methodfor a mobile terminal based on eyeprint recognition and an imageexposure system, where the image exposure method includes: acquiringimage data through a camera when it is detected that the mobile terminalturns on the eyeprint recognition; positioning an eyeball positionthrough image processing, and acquiring a brightness parameter of theeyeball position; and according to the acquired brightness parameter,querying a prestored exposure parameter corresponding to the brightnessparameter, adjusting the exposure parameter, and exposing the eyeballposition according to the adjusted exposure parameter. According to thepresent invention, in the process of eyeprint recognition, a regionexposure method is used for a user's eyeball exposure to control theexposure, so that the eyeprint recognition speed is improved, theunlocking is safer and more convenient, and convenience is provided forthe user.

It is to be understood that application of the present invention is notlimited to the foregoing examples, those of ordinary skill in the artmay make improvements or transformations according to the foregoingdescription, and all these improvements and transformations should fallwithin the scope of protection of the appended claims of the presentinvention.

1. An image exposure method for a mobile terminal based on eyeprintrecognition, comprising: detecting whether eyeprint recognitionunlocking is started or not; if the eyeprint recognition unlocking isstarted, turning on a camera to acquire a user's face image and displayby preview the acquired face image on a display screen; processing theface image by using eyeprint recognition software to position an eyeballat an eyeball position of the face image; acquiring a brightnessparameter of the eyeball position; querying a prestored exposureparameter corresponding to the acquired brightness parameter, andadjusting the queried exposure parameter so that a brightness of animage exposed by using the adjusted exposure parameter is 128gray-levels; exposing the eyeball position based on the adjustedexposure parameter; and matching an eyeprint image acquired after anexposure with prestored eyeprint data, and unlocking the mobile terminalif the matching succeeds, or prompting a failure in the unlocking of themobile terminal if the matching fails.
 2. The image exposure method fora mobile terminal based on eyeprint recognition according to claim 1,including increasing a signal amplification factor and exposure time ifthe acquired brightness parameter is less than 128 gray-levels; anddecreasing the signal amplification factor and the exposure time if theacquired brightness parameter is greater than 128 gray-levels.
 3. Animage exposure method for a mobile terminal based on eyeprintrecognition, including: acquiring image data through a camera when it isdetected that the mobile terminal turns on the eyeprint recognition;positioning an eyeball at an eyeball position, and acquiring abrightness parameter of the eyeball position; querying a prestoredexposure parameter corresponding to the acquired brightness parameter,adjusting the exposure parameter, and exposing an eyeball at the eyeballposition according to the adjusted exposure parameter.
 4. The imageexposure method for a mobile terminal based on eyeprint recognitionaccording to claim 3, including: acquiring in advance and storing acorresponding relation among a user's eyeprint data, the acquiredbrightness parameter and the adjusted exposure parameter.
 5. The imageexposure method for a mobile terminal based on eyeprint recognitionaccording to claim 4, including: verifying an image acquired afterexposure with prestored eyeprint data to unlock the mobile terminal. 6.The image exposure method for a mobile terminal based on eyeprintrecognition according to claim 5, including: querying a prestoredexposure parameter corresponding to the brightness parameter; decreasingor increasing exposure time and signal amplification factor according toa corresponding relation; and exposing the eyeball at the eyeballposition according to an adjusted exposure parameter.
 7. The imageexposure method for a mobile terminal based on eyeprint recognitionaccording to claim 3, wherein the exposed eyeball may be a left eyeor/and a right eye.
 8. An image exposure system for a mobile terminalbased on eyeprint recognition, comprising: a detecting and acquiringmodule, configured to acquire image data through a camera when it isdetected that the mobile terminal turns on the eyeprint recognition; apositioning module, configured to position an eyeball at an eyeballposition, and acquire a brightness parameter of the eyeball position;and an adjusting and exposing module, configured to query a prestoredexposure parameter corresponding to the acquired brightness parameter ofthe eyeball position, adjust the prestored exposure parameter, andexpose an eyeball at the eyeball position according to the adjustedexposure parameter.
 9. The image exposure system for a mobile terminalbased on eyeprint recognition according to claim 8, including: aprestoring module, configured to acquire in advance and store acorresponding relation among a user's eyeprint data, the acquiredbrightness parameter of the eyeball position and the prestored exposureparameter.
 10. The image exposure system for a mobile terminal based oneyeprint recognition according to claim 9, including: a verifying andunlocking module, configured to verify an image acquired after exposurewith prestored eyeprint data to unlock the mobile terminal.
 11. Theimage exposure system for a mobile terminal based on eyeprintrecognition according to claim 10, wherein the adjusting and exposingmodule includes: a querying unit, configured to query the prestoredexposure parameter corresponding to the acquired brightness parameter ofthe eyeball position; an adjusting unit, configured to decrease orincrease exposure time and a signal amplification factor according to acorresponding relation; and an exposing module, configured to expose theeyeball at the eyeball position according to the adjusted exposureparameter.
 12. The method of claim 1, wherein an alternate password isactivated in response to a failure of the system to unlock the mobileterminal with the first password.
 13. The method of claim 1, wherein theeyeprint image is formed from two sides of a person's iris.
 14. Themethod of claim 2, including determining whether to increase theexposure time based on a difference between a value of the acquiredbrightness parameter and a target brightness value.
 15. The method ofclaim 3, wherein an alternate nine-grid pattern is activated to unlockthe camera in response to a failure of the system to unlock the mobileterminal with a first nine-grid pattern.
 16. The method of claim 5,including determining whether to increase the exposure time based on adifference between a value of the acquired brightness parameter and atarget brightness value.
 17. The method of claim 3, wherein the eyeprintimage is formed from two sides of a person's iris.
 18. The system ofclaim 8, wherein the system activates an alternate password in responseto a failure of the system to unlock the mobile terminal with the firstpassword.
 19. The system of claim 11, wherein the system determineswhether to increase the exposure time based on a difference between avalue of the acquired brightness parameter of the eyeball position and atarget brightness value.
 20. The system of claim 11, wherein the systemdetermines whether to increase the signal amplification factor based ona difference between a value of the acquired brightness parameter of theeyeball position and a target brightness value.